International Cowden Consortium operational criteria for the diagnosis of CS, Ver 2000
| Pathognomonic criteria |
| Mucocutaneous lesions |
| Trichilemmomas, facial |
| Acral keratoses |
| Papillomatous papules |
| Mucosal lesions |
| Major criteria |
| Breast carcinoma |
| Thyroid carcinoma (non-medullary), especially follicular thyroid carcinoma |
| Macrocephaly (megalencephaly) (say, ⩾95th centile) |
| Lhermitte-Duclos disease (LDD) |
| Endometrial carcinoma |
| Minor criteria |
| Other thyroid lesions (eg, adenoma or multinodular goitre) |
| Mental retardation (say, IQ ⩽75) |
| GI hamartomas |
| Fibrocystic disease of the breast |
| Lipomas |
| Fibromas |
| GU tumours (eg, renal cell carcinoma, uterine fibroids) or malformation |
| Operational diagnosis in a person |
| (1) Mucocutaneous lesions alone if: |
| (a) there are 6 or more facial papules, of which 3 or more must be trichilemmoma, or |
| (b) cutaneous facial papules and oral mucosal papillomatosis, or |
| (c) oral mucosal papillomatosis and acral keratoses, or |
| (d) palmoplantar keratoses, 6 or more |
| (2) 2 major criteria but one must include macrocephaly or LDD |
| (3) 1 major and 3 minor criteria |
| (4) 4 minor criteria |
| Operational diagnosis in a family where one person is diagnostic for Cowden syndrome |
| (1) The pathognomonic criterion/ia |
| (2) Any one major criterion with or without minor criteria |
| (3) Two minor criteria |
Operational diagnostic criteria are reviewed and revised on a continuous basis as new clinical and genetic information becomes available.